'Mean Response' Disregards the Importance of Individual Variation (Commentary‪)‬

The conventional approach in the field of exercise science is to report the response to interventions as the mean (average) of the intervention group. While the mean may be a convenient measure, it fails to consider the significant individual variation present in all aspects of human biology, resulting in findings that are at best simplistic and, at worst, misleading. Several authors have highlighted the discrepancy between the mean group response and the responses of individual participants by reporting the effects of exercise training programmes that were carefully standardised by frequency and intensity of training. (1-6) These standardised training studies have documented a range of responses in parameters, including maximal oxygen uptake (V[O.sub.2max]), (1,3-6) exercise heart rate, (1,5) resting heart rate, (5) individual anaerobic threshold, blood pressure, (1) HDL-cholesterol, (1) resting respiratory exchange ratio (RER), (2) body composition (2) and performance. (6) A particularly interesting example comes from Hautala et al., (3) who measured the change in V[O.sub.2max] after 2 weeks of endurance training. Seventy-three sedentary males and females completed the training, and, while the mean response was an improvement of 8 [+ or -] 6%, individual values ranged from a 5% reduction in V[O.sub.2max] to a 22% improvement, with an even distribution of responses in between.